Some quinones such as 1,4-benzoquinone 2, 1,4-naphthoquinone 3 and 1,2-naphthoquinone 4 dissolved in diethylamine were irradiated with 300 nm UV light to afford red aminoquinones 6, 7, and 9 as the major products. Irradiation of a solution of a primary product, i.e., 2,5-bis(diethylamino)-1,4-benzoquinone 6 in benzene gave 2,5-bis (ethylamino)-1,4-benzoquinone 10 in 80% yield, along with an oxazoline 11 in 19% yield via photochemical deethylation. A solution of 2-diethylamino-1,4-naphthoquinone 7 in benzene was also irradiated under the same condition, in which 2-ethylamino-1,4-naphthoquinone 12 was obtained in ca. 100% yield.